Khan, Misbahul Ain; Ribeiro, Vera Lucia Teixeira, Pakistan Journal of Scientific and Industrial Research 43 (2000) 168-170 describes the synthesis of benzimidazo[1,2-a]benzimadozoles
(R=H, Me, Et) by trialkyl phosphite-induced deoxygenation and thermolysis of 1-(o-nitrophenyl)- and 1-(o-azidophenyl)benzimidazoles.
Pedro Molina et al. Tetrahedron (1994) 10029-10036 reports that aza Wittig-type reaction of bis(iminophosphoranes), derived from bis(2-aminophenyl)amine with two equivalents of isocyanate directly provided benzimidazo[1,2,a]benzimidazole derivatives.
(R=R′=
R=
and R=
R=iso-propyl and R′=ethyl)    Kolesnikova, I. V.; Zhurnal Organicheskoi Khimii 25 (1989) 1689-95 describes the synthesis of 5H-benzimidazo[1,2-a]benzimidazole 1,2,3,4,7,8,9,10-octafluoro-5-(2,3,4,5,6-pentafluorophenyl).
    Achour, Reddouane; Zniber, Rachid, Bulletin des Societes Chimiques Beiges 96 (1987) 787-92 describes the synthesis of benzimidazobenzimidazoles
(R=H, —CH(CH3)2) which were prepared from benzimidazolinone derivatives.    Hubert, Andre J.; Reimlinger, Hans, Chemische Berichte 103 (1970) 2828-35 describes the synthesis of benzimidazobenzimidazoles
(R=H, CH3,
JP2001160488 describes an electroluminescent element which has a light-emitting layer having a single-layer or multiple-layer organic compound film between opposing anode and cathode, wherein at least one layer of the organic compound film contains at least one kind of compounds indicated by formula
The following compounds are explicitly disclosed:

US20100244006 relates to an organic electroluminescent device which includes: a cathode; an anode; and at least one organic layer between the cathode and the anode. The at least one organic layer includes a light emitting layer containing at least one light emitting material. A compound represented by the following formula
is contained in the at least one organic layer. where n stands for an integer of 2 or greater, L represents an n-valent linking group, and R1, R2, R3, and R4 each independently represents a hydrogen atom or a substituent.
The compounds described in US20100244006 are preferably used in as host in the light emitting layer.
represents an example of a compound disclosed in US20100244006.
KR1020110008784 relates to novel organic luminescent compounds of formula
and organic electroluminescence devices including the same.
US2005079387 relates to an imidazole ring containing compound of formula Ar1-Ar2-Ar3, (blue luminescent host compound) and an organic electroluminescence (EL) display device using the same.
Ar2 is selected from the group consisting of
each of Ar1 and Ar3 is independently selected from
wherein X′ is O, or S.
US2005074632 relates to an imidazole ring containing compound of formula
and an organic electroluminescence (EL) display device using the same. In particular, the imidazole ring-containing compound may be used alone or in combination with a dopant as a material for organic films such as an electroluminescent layer.
A is selected from the group consisting of
—N(R13R14), and
B is selected from the group consisting of
X is selected from the group consisting of —O—, —S—, —Se— and —NH—.
JP2007180147 relates to an organic electroluminescence element, sandwiched by an anode and a cathode and containing at least a light-emitting layer, which contains a compound represented by general formula 1, 2, 3 or 4:
Ar1-Ar4=aromatic group or aromatic heterocyclic group; R1-R5=H or substituent; Z1=residue required to form heterocyclic ring of 5 or 6 members; L1, L2=bond or coupling group; and X1-X16=carbon or nitrogen. A new ring can be formed in one portion of Ar1 and Ar2, and Ar3 and Ar4.
The following compounds are explicitly disclosed:

U.S. Pat. No. 6,551,723 relates to an organic electroluminescence element comprising a light-emitting layer or a plurality of organic compound thin layers containing a light-emitting layer between a pair of electrodes, wherein at least one layer in the organic electroluminescence element comprises at least one heterocyclic compound represented by formula (I) to (VII):
R11, R12, R13, R21, R22, R31, R32, R41, R42, R51, R61, and R71 are each independently a hydrogen atom or substituent; Z1, Z2, Z3, Z4, Z5, Z6, and Z7 are a group of atoms that are necessary for forming a 5- or 6-member ring. The compounds represented by formula (I) to (VII) are particularly added to a light-emitting layer and/or electron injection/transporting layer. The following compounds are explicitly disclosed:

WO2011160757 relates to an electronic device comprising an anode, cathode and at least one organic layer which contains a compound of formulae
wherein X may be a single bond and L may be a divalent group. The following 4H-Imidazo[1,2-a]imidazole compounds are explicitly disclosed:

Notwithstanding these developments, there remains a need for organic light emitting devices comprising new hole transport materials to provide improved efficiency, stability, manufacturability, and/or spectral characteristics of electroluminescent devices.